Refuges of non-Bacillus thuringiensis (Bt) cotton are used to delay Bt resistance in several key insect pests. In 2004, I discovered that Bt cotton plants sometimes enter refuges via the seed bag, and hypothesized that this type of gene flow could have important effects on resistance evolution in insect pests. In the research described herein, I investigated the sources of Bt plants in the non-Bt cotton seed supply and assessed the potential implications of this gene flow on pest resistance evolution. I report results from an empirical study of gene flow in 15 non-Bt cotton seed production fields, as well as results from simulation modeling studies of gene flow from one-toxin and two-toxin Bt cotton. The current policy on gene flow from genetically engineered crops in the United States is also reviewed, including the implications of my research findings for policymakers. Key findings of this study included the prominent role of seed-mediated gene flow in the seed-production setting, and the utility of a geographic information system (GIS) ring analysis approach for describing pollen-mediated gene flow in cotton fields. Modeling results indicated that high rates of gene flow of Bt cotton into refuges could have large effects on pest resistance evolution under certain sets of assumptions, particularly in parts of the world where farm-saved seed is planted year after year in cotton fields. It appears that some of these effects could be mitigated by using non-cotton refuges or by using plants that contain linked transgenes that confer multiple toxins. There are no clear regulations in the United States regarding gene flow of Bt cotton into refuge seed or into seed production fields of non-Bt cotton, as Bt cotton has been deregulated following extensive safety testing. Nevertheless, results from this research suggest that limiting gene flow into refuge seed could be important for sustaining the efficacy of Bt cotton against targeted insect pests in regions where refuges are used.

An easy and reliable way to join two or more components is to use a bolted joint. When torque is applied on the bolt head, a clamp force is achieved. However about 90% of this torque will be used just to overcome the friction in the interfaces. To be able to fasten these in an ecient and precise manner the friction in the bolt threads and underhead area is important to understand. This is currently investigated at Atlas Copco by using a friction test rig, FTR, which measures the clamp force, the total torque and the shank torque. To evaluate the test rig and also to be able to evaluate dierent friction models, a parameterised simulation model of a bolted joint is built. This is a 3D-model of the joint containing a bolt, a nut and a test specimen. The stiness and frictional behaviour of the FTR is used in the model to get a good comparison between these two. Dierent contact formulations and settings are tested to achieve a good model. Also, mesh size, step size and material models are evaluated to see the eect of these. The results show a good correlation between the FTR data and the simulation model. For the total torque to clamp force ratio a dierence of about 1% is achieved. The average dierence in shank torque and underhead torque is at 3.1% and -1.6% respectively. The pressure distribution for this model is shown to be unevenly distributed along the threads. This is minimized by softening the contact, but this instead increases the error between the FTR data and the simulation model. For the evaluation of friction models that are based on the contact pressure this needs to be investigated further to nd a good compromise between the contact pressure and the frictional behaviour.

Simulation is a process that allows evaluation of a system from a comprehensive viewpoint. Thanks to this modern approach it is possible to find weak spots or other problems and solve them in the simulation model before applying the solution in a real situation. In my thesis I will focus on creating a simulation model of the production line of a Czochralski chamber in a specialized software named Simul8. Furthermore, I will deal with analysis of the various processes and the utilization of personnel involved in the production. I will also try to eliminate problems and discrepancies that show up by experimenting with the model. Based on the final results I will create recommendations that could help improve the real situation in the company.

Documento Confidencial. Não pode ser disponibilizado para consulta / Tese de mestrado. Engenharia Informática. Faculdade de Engenharia. Universidade do Porto. 2007

Particleboard (PB) is a widely used panel material because of its physical properties and low cost. Unfortunately, cutting can degrade its surface creating rejects and increasing manufacturing costs. A major challenge is PB’s internal variability. Different particle and glue bond strength combinations can sometimes create high quality surfaces in one area and defects such as edge chipping in nearby areas. This research examines methods of improving surface quality by examining PB characteristics and their interactions with the cutting tool. It also develops an analytical model and software tool that allows the effects of these factors to be simulated, thereby giving practical guidance and reducing the need for costly experiments. When PB is cut and the glue bond strength is weaker than the particle strength, particles are pulled out, leading to surface defects. When instead the glue bond strength is stronger than the particle strength, particles are smoothly cut, leading to a high quality surface. PB is modeled as a matrix of particles each with stochastically assigned material and glue bond strengths. The PB model is layered allowing particles to be misaligned. Voids are modeled as missing particles. PB cutting is modeled in three zones. In the finished material and tool tip zones, particles are compressed elastically and then crushed at constant stress. After failure, chip formation occurs in the chip formation zone. At large rake angles, the chip is modeled as a transversely loaded beam that can fail by cleavage at its base or tensile failure on its surface. At small rake angles, the chip is modeled as the resultant force acting on the plane from the tool tip through to the panel surface. Experimental and simulation results show that cutting forces increase with depth of cut, glue content and particle strength. They decrease with rake angle. Glue bond strength can be increased to the equivalent particle strength through the selection of particle geometry and the subsequent increased glue bond efficiency, which increases the cut surface quality without the need for additional glue. Minimizing the size and frequency of voids and using larger rake angles can also increase surface quality.

Congestion on the road is identified as a severe threat to nations’ economy. To address this problem, in the past the capacity of existing infrastructure is increased by building new roads. But as history has shown, it is not only an expensive and unsustainable, but also not an efficient way of dealing with this problem. Alternatively, by identifying underutilized links, for example, in the form of parallel routes, the already existing infrastructure can often be used more efficient. This thesis focuses on the development of a framework to simulate re-routing incentives to enable an improved travel corridor performance. Thus, the effects of providing traveler information and tendering mometary incentives on a concidor’s traffic flow are investigated. The aim is to show that by changing the route choice behavior of a certain percentage of the fleet, the overall performance of the existing corridor can be increased. By using the microscopic traffic simulation tool VISSIM in combination with dynamic traffic modeling, numerous scenarios are simulated. By gradually increasing the amount of users who get access to the incentive scheme, the impacts of the penetration get analyzed as well. Based on a network stretch located in California, United States, the simulation model is developed. Using this model, three different scenarios are investigated in detail: a No Incident scenario, a Construction Work scenario and an Accident scenario. Finally, a comprehensive analysis of the simulation results takes place. It mainly focuses on the indicator travel time to discuss the impacts on the corridor performance. Interpreting the achieved simulation results, it can be stated that already small penetration rates have the potential for a significant increase of the corridor performance. To be able to optimize the corridor’s performance, free capacity on detours – especially  at bottlenecks like ramps – has to be available. Nevertheless, in case of high penetration rates, straightforward broadcasting of incentives is not an option.

Purpose: The goal of this study is to emphasize the use of business simulation as a learning tool in educational institutions.  For instance, the two master’s programs (marketing & entrepreneurship, provided by Umeå Business School at master’s level), comprised of four core courses each, but only one module out the four provided utilized simulation for learning purpose. Generally self study, class lectures and case studies are used as the main pedagogy tools in the class room setting. In case of Umeå Business School, the use of simulations and gaming was rather limited in Umea School of Business (USBE) despite the fact that simulations are used to the point of saturation in American universities. This research is focused towards exploring the perceptions of students who undertook a business simulation at Umeå Business School, Sweden. Furthermore, it also provides a model for an effective simulation from educational point of view. Method: Hypotheses were developed to investigate the perceptions held by the students at USBE regarding their perceived effectiveness of simulation as a learning tool. A deductive approach was followed by using theories and scientific research by which hypotheses were generated and tested for answering the literature gaps. Quantitative research strategy was used and questionnaires were sent only to qualified respondents (those students of USBE who had already taken simulation at least once in any modules of their study tenure). Hypotheses were generated to find out correlations between the variables and tested through Pearson coefficient using SPSS testing methods. Findings/conclusion: The findings revealed that students consider simulation the most learning tool compared to others. Simulation is considered practical learning, learning through a gaming approach, an exercise that replicates realistic environment in class room. It provides an enjoyable way of learning and the retention of learnt concept is in high to medium range. Empirical findings show that there is a positive correlation between the variable students who would like to use simulation again with the variable that students will register a course which provides simulation. There is a strong positive correlation among variable of perceiving simulation as exciting and variable perceiving it as a fun way of learning.   Positive correlation exists among variables of being excited to know of simulation in a course and variable of considering simulation being a learning experience.   Lastly we found that there is positive and highest correlation in perception of students regarding likeness and learning with regards to simulation.  This means that compared to other tools there is more likeness of simulation amongst students and they perceive it as most learning tool compared to class lectures, guest lectures, self study and group discussions.    The study concluded with providing a basic model of an effective simulation which was developed in line with literature review and empirical findings from this research

The trends of present design in electronic systems are towards high speed, small size, and lower voltage levels. Due to these trends, the influence of ESD becomes a more serious problem for an EMC designer. How to precisely evaluate the effect of ESD by measurement and simulation, and try to solve these questions quickly is the most important topic at present. In this thesis we introduce several measurement approaches to ESD. We try to find the equivalent circuit model of the ESD gun operated in our lab, and construct the simulation model by Agilent ADS software. Good agreement between simulation and measurement demonstrates the correctness of the model for this ESD gun. By combining the simulation model of ESD gun with equivalent circuit of DUT extracted by Ansoft Q3D software, it is found this method can evaluate the ESD phenomena of DUT fast and precisely. In addition, with this method some phenomena restricted by measurement can be studied. Finally two real products including a PDA (floating system) and the mainboard in the desktop computer system (grounding system) are discussed in detail.

This study utilized (a) actual measured agricultural water use along with (b) geostatistical techniques, (c) crop simulation models, and (d) general circulation models (GCMs) to assess irrigation demand and the uncertainty associated with demand projections at spatial scales relevant to water resources management. In the first part of the study, crop production systems in Southwest Georgia are characterized and the crop simulation model error that may be associated with aggregated model inputs is estimated for multiple spatial scales. In the second portion of this study, a methodology is presented for characterizing regional irrigation strategies in the Lower Flint River basin and estimating regional water demand. Regional irrigation strategies are shown to be well represented with the moisture stress threshold (MST) algorithm, metered annual agricultural water use, and crop management data. Crop coefficient approaches applied at the regional scale to estimate agricultural water demand are shown to lack the interannual variability observed with this novel approach. In the third portion of this study, projections of regional agricultural demand under climate change in the Lower Flint River basin are presented. GCMs indicate a range of possible futures that include the possibility of relatively small changes in irrigation demand in the Lower Flint River basin. However, most of the GCMs utilized in this work project significant increases in median water demand towards the end of this century. In particular, results suggest that peak agricultural water demands in July and August may increase significantly. Overall, crop simulation models are shown to be useful tools for representing the intra-annual and interannual variability of regional irrigation demand. The novel approach developed may be applied to other locations in the world as agricultural water metering programs become more common.

A computer simulation model of the table contact phase of gymnastics vaulting was developed to gain an understanding of the mechanics of this phase of the vault. The model incorporated a gymnast and a vaulting table, and used a novel two-state contact phase representation to simulate the interaction between these two bodies during the table contact phase. The gymnast was modelled in planar form using seven segments, with torque generators acting at the wrist, shoulder, hip and knee joints. The model also allowed for shoulder retraction and protraction, displacement of the glenohumeral joint centre and flexion/extension of the fingers. The table was modelled as a single rigid body that could rotate. The model was personalised to an elite gymnast so that simulation outputs could be compared with the gymnast's performance. Kinematic data of vaulting performances were obtained using a optoelectronic motion capture system. Maximal voluntary joint torques were also measured using an isovelocity dynamometer, and a torque - angle - angular velocity relationship was used to relate joint torques to joint angles and angular velocities. A set of model system parameters was determined using a gymnast-specific angle-driven model by matching four simulations to their respective performances concurrently. The resulting parameters were evaluated using two independent trials, and found to be applicable to handspring entry vaults. The torque-driven model was successfully evaluated, and shown to produce realistic movements, with mean overall differences between simulations and recorded performances of 2.5% and 8.6% for two different handspring entry vaults. The model was applied to further understanding of the mechanics of the table contact phase of gymnastics vaulting. Optimisation showed that there was limited potential (1.3%) for the gymnast to improve performance through technique changes during the table contact phase. However, with additional changes in configuration at table contact post-flight rotation could be increased by 9.8% and post-flight height could be increased by 0.14m. Angular momentum was found to always decrease during the table contact phase of the vault, although the reductions were less when maximising post-flight rotation.